Pro-Russian Gubarev, a symbol of east Ukraine separatism

For some, Pavel Gubarev's name has become a symbol of resistance against the new pro-European powers in Kiev. For others, he represents a threat to a united Ukraine.

Since his appearance on the political stage just a week ago, the tough-looking Gubarev, who turns 31 on Monday, has fired up the imagination of separatist forces in the eastern Ukrainian city of Donetsk, the former stronghold of ousted pro-Russian president Viktor Yanukovych.

His face now appears on placards at rallies pushing for Donetsk to join Russia and his release from detention, following his arrest last Thursday on separatism charges, has become the movement's chief demand.

Gubarev, a local advertising executive, first grabbed attention on March 3 when he took over the regional government building in Donetsk with pro-Russian forces and proclaimed himself the "people's governor."

Denouncing Ukraine's new government, in power since the ouster last month of the pro-Moscow regime, he brushed aside the governor appointed by Kiev, Sergiy Taruta.

However, his calls for a referendum in Donetsk -- like the one on March 16 that Crimea's authorities hope will see them rejoin Russia -- prompted an investigation against him for "threatening the territorial integrity" of Ukraine.

On Thursday, police arrested him at his home while he was being followed by a crew from LifeNews, a Moscow website and TV channel with close links to Russia's security services, fueling rumours that he has close ties to the Kremlin.

- Gubarev rise 'totally unexpected' -

For many, the fast rise of Gubarev -- an amateur boxer who had previously only been known in Ukrainian business circles -- was something of a surprise.

"He didn't represent any group and his emergence as the organiser of mass protests has been totally unexpected," said Donetsk's deputy mayor Sergiy Bogachev, who hoped things would quiet down following his arrest.

Gubarev already spoke out violently to friends and on social networks in the last few months against the Maidan protesters who stood up against Yanukovych's government in Kiev.

"He believes in unity for the Slavic people, it's an issue he has thought about a lot," said a close acquaintance of Gubarev who refused to be named.

"He believes in what he's doing. He is not crazy."

Gubarev's arrest has now galvanised his most loyal supporters, who are demanding his release. Thousands of people cheered his name during a pro-Russian protest held on Donetsk's central Lenin Square on Saturday.

"Pavel expressed his opinion and that's why he's in prison," said Robert Donia, who describes himself as Gubarev's deputy.

Hailing from a big family and himself the father of three, Gubarev was previously a militant member of the Progressive Socialist Party of Ukraine, whose programme rejects all things Western -- globalisation, the United States or the International Monetary Fund -- and campaigns to join Russia.

Formed in the 1990s, the party gained a following in southeastern Ukraine and Crimea, but lost much of it over the last 10 years.

Ukraine has long been split between an eastern and southeastern part backing closer ties with Moscow and a more pro-European western Ukraine.

Gubarev now risks 10 years in prison but Gubarev's wife, in an interview to LifeNews that amounted to her only public appearance, vowed to "continue the fight" on his behalf.